Researchers believe it could offer hope to people who have suffered spinal cord injuries, strokes and other conditions where they will need to regain strength, mobility and independence.

Scientists, led by neuroscientist Miguel Nicolelis of Duke University in North Carolina, used a virtual reality system that worked with the patients' own brain activity to simulate control of their legs during the long-term training programme. The first hopeful signs were spotted in some patients after seven months, but the sensations and muscle control reported by four patients were so strong after a year that their doctors upgraded their diagnoses from complete to partial paralysis.

Among those who took part in the rehabilitation training, five people had been paralysed for at least five years, while two had been paralysed for more than a decade.

Most patients said they had better bladder control and bowel function, which meant they could cut back on much-needed laxatives and catheters.

This in turn is encouraging for other patients, as these changes reduce the risk of common infections and causes of death in people with chronic paralysis, according to Mr Nicolelis.

"What we're showing in this paper is that patients who used a brain-machine interface for a long period of time experienced improvements in motor behaviour, tactile sensations and visceral functions below the level of the spinal cord injury," he said.

"Until now, nobody has seen recovery of these functions in a patient so many years after being diagnosed with complete paralysis."

Previous successes from The Walk Again Project include Julian Pinto, a young paraplegic man, being able to kick a football during the 2014 World Cup opening ceremony by using a brain-controlled robotic exoskeleton.

The patients worked with different training systems, including the exoskeleton Mr Pinto wore at the 2014 World Cup.